Chunk #11 — Activation of metabotropic glutamate receptors (mGluRs) or muscarinic Ach receptors (mAchRs) induces rhythmic bursting at α/θ frequencies in TC neurons
Recently, we found that activating metabotropic gluatamate receptors (mGluRs), either pharmacologically or via electrically stimulating corticothalamic fibres, led to around 25% of TC neurons in the cat LGN recorded in vitro exhibiting a third mode of firing which we termed high-threshold (HT) bursting (Fig. 1A, bottom) (Hughes et al. 2002, 2004). HT bursting occurs rhythmically at ~3–15 Hz, thus encompassing both the α (8–13 Hz) and θ (4–7 Hz) bands, and unlike LTCP-mediated bursting is present when neurons are relatively depolarized (>−55 mV) (Hughes et al. 2002, 2004; Hughes and Crunelli 2005). Importantly, single unit recordings of LGN TC neurons from freely moving cats showed that activity with indistinguishable properties to HT bursting occurs coherently with α oscillations in the intact brain (Hughes et al. 2004; Hughes and Crunelli 2005, 2007). We have since found that following an equivalent activation of mGluRs, HT bursting with broadly similar properties to those noted in the cat LGN can also be observed in other areas of the cat thalamus, including the the ventrolateral (VL) nucleus, i.e. the motor thalamus, and the ventrobasal complex
